I've watched a lot of talks from Elon Musk recently (the successful entrepreneur behind Tesla, SpaceX, etc.) and apparently he makes a lot of decisions based on odds of success. You could look back at all those years you've made a resolutions list and ask yourself : how many times have you successfully accomplished every items of this list and persisted in the changes it has bring to your life ? Then calculate the odds of success this year. If your odds looks bad, just stop it, stop doing what does not work.
I believe if we are unable to persist in our "yearly good intentions" is because we don't have a goal. Our resolutions are just a reflect of what we would change right now to feel better (at least, in my case), but this is temporary and leads no where.
What I will do this year is describing (on paper) the portrait of the self I want to be, and the life I want to be in. It's like, imagining your self in the future (a successful future) in which you would be happy and fulfilled. And don't limit yourself to what you can accomplish, if you want to be an astronaut but don't see how you could do that right now, write it down anyway. This self portrait should represent everything you aspire to be.
Once you've done that, now you have a goal.
But you don't have a plan yet ! This plan is built gradually by looking at your idealized self portrait and asking yourself : what can I do right now to advance in the direction of my goal ? You'll find little things you can do that will slowly pull you toward your goal and hopefully you'll find more and more things along the way.
It's basically a flexible and adaptative plan toward a more static objective. And according to this TED talk, it might contribute to your success.
Keep looking at the odds of success too, if you have multiple projects you want to do, calculate which one has the most chances of bringing you closer to your goal, and do this one first.
By applying this technique, you'll always have an eye on the reason why you are doing all this and it will be easier to not loose yourself along the way.